Which Has The Greater Impact On Global SST Anomalies, The Rise In The SST Anomalies Of The Arctic Ocean Or The Decrease In The Southern Ocean?

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This post illustrates an observation I’ve made a number of times while investigating other subjects, so I thought I’d post it. It shows the relative strengths of the polar SST anomalies.

Using the NCDC’s Optimum Interpolation (OI.v2) SST Anomaly dataset, which begins in November 1981, the Arctic Ocean shows a significant positive linear trend. Refer to Figure 1. Over the same period, the Southern Ocean shows a negative linear trend that’s much less significant. The latitudes I’ve used for the Arctic Ocean are 65N-90N, while the Southern Ocean latitudes are 90S-60S.http://i43.tinypic.com/2e4m62r.png
Figure 1

According to Wikipedia, the area of the Arctic Ocean is 14,056,000 sq. km. The Southern Ocean, on the other hand, has an area of 20,327,000 sq. km or about 45% larger than the Arctic Ocean. Sea ice also varies in the polar oceans, as is well known.

Taking those factors into consideration, which plays a greater role in global SST anomaly trends, the rise in the Arctic Ocean SST anomalies, or the drop in the Southern Ocean SST anomalies?

The easiest way to illustrate it is to compare global SST anomalies with and without the polar oceans. (Or someone other than me could go through all of the calculations to factor in area, monthly sea ice extent, etc., using polar ocean data.) If the rise in the SST anomalies of the Arctic Ocean is having the greater impact on global SST anomalies than the drop in the Southern Ocean data, then the Global SST anomaly dataset including the polar oceans would have a higher trend than the a global dataset without the polar oceans. Refer to Figure 2. The opposite takes place.http://i44.tinypic.com/10ngtnr.png
Figure 2

While the two linear trends are close, the drop in the Southern Ocean SST anomalies has the greater effect. That is, adding the polar oceans to the data caused the global SST anomaly trend to decrease.

Someone will note that the latitudes of the Arctic and Southern Ocean datasets are not the same. The Southern Ocean is generally defined as the ocean south of 60S. But the Arctic Ocean borders aren’t defined by one latitude. Does this skew the results? Since the NOAA NOMADS system requires latitudes and longitudes as inputs, I can’t customize the Arctic Ocean borders. But I can extend the latitudinal range to 60N-90N. Same results. The linear trend of the dataset without the polar data has the higher linear trend, though the gap is closing.http://i40.tinypic.com/15nrj9f.png
Figure 3

Bob-From what I understand the Arctic Ocean SST data is highly suspect due to the sea ice retreat allowing new gridcells to come in that had zero data before. They have nothing but short strings of positive anomalies with nothing but fixed values in the base period.

Andrew: The Arctic presents a unique problem: how to address the simple fact that some years the ice melt is greater than others, exposing more sea surface. There is no base period for anomalies, since it’s brand spanking new data. I don’t know that there’s a correct way to address it. Each of the SST anomaly datasets appears to take a different approach. http://i44.tinypic.com/aop74g.png

(Note the unusual 12-month shift, 1996, in the ERSST.v3b data. I’ll have to call that to their attention. Looks like a glitch.)

Przemysław Pawełczyk: You asked, "...where would the energy from PWP dissipate (if it realy happened)?"

As you know, much of the decline in Sea Level anomaly in the PWP is caused by the shifting of the warm water east during the El Nino. Some of it is caused by the change (reversal/decline) in trade winds. During the transfer from El Nino to La Nina over the next six to nine months, the PWP will regain much of decline as the warm water sloshes back to the west.

The east and west equatorial Pacific Warm Water Volume data from the TAO project website illustrates this pretty well:http://www.pmel.noaa.gov/tao/elnino/wwv/gif/compa_ew.gif

They run a little out of synch at times and with the latest data, the eastern equatorial Pacific appears to have peaked while western equatorial Pacific has not. The west looks like it's still declining.

Here's a link to the WWV graphs page from the TAO project:http://www.pmel.noaa.gov/tao/elnino/wwv/

Comment Policy, SST Posts, and Notes

Comments that are political in nature or that have nothing to do with the post will be deleted.####The Smith and Reynolds SST Posts DOES NOT LIST ALL SST POSTS. I stopped using ERSST.v2 data for SST when NOAA deleted it from NOMADS early in 2009.

Please use the search feature in the upper left-hand corner of the page for posts on specific subjects.####NOTE: I’ve discovered that some of the links to older posts provide blank pages. While it’s possible to access that post by scrolling through the history, that’s time consuming. There’s a quick fix for the problem, so if you run into an absent post, please advise me. Thanks.####If you use the graphs, please cite or link to the address of the blog post or this website.